I remember WebOS, but it has been a long time since I have seen it on anything. I would not be at all surprised if the person who created the gestures had never seen it. That is one of the biggest issues we have in Computer Science, a lack of history.
No, what it does mean is that just because they did something and someone else did it later, that it was copied from them. Some features Apple takes from Google, some Google takes from Apple, some are developed in parallel independently, but having been in a similar world may turn out similarly, some were found in older systems and are completely original. WebOS never had enough market share to argue that everyone would have seen it and therefore ideas that are similar to it came from it. In Latin it is: Post hoc, ergo propter hoc. It is possible the UI guys saw it, it is also possible they both studied with the same design professors and had the same influences. Hard to know.